The surface acoustic wave (SAW) device can be used to measure temperature wirelessly, which is highly adaptable to the use in aero-engines high-temperature test scenarios where wired-sensors is not suitable for its difficulty in signal transfers. Herein, this paper presents a SAW sensor capable of achieving high-temperature measurement up to 800 °C with a good repeatability. The sensor is built on 41°Y LiNbO 3 substrate with a SiO 2 passivation. With the protection of SiO 2 layer, the volatilization of platinum is effectively prevented to ensure SAW's stability at a higher temperature. At the same time, SiO 2 layer also protects the lithium niobate substrate, according to our verification result of XRD and EDS. Both crystal orientation and chemical composition of LiNbO 3 substrate have been maintained after high-temperature testing. The temperature coefficient factor TCF is -2.98KHz/°C for our passivated SAW devices with a good linearity and repeatability.